This invention relates to a pushbutton switch comprising a switch button having a contact member with conductivity and a base plate molded integrally with the switch button.
As a method to connect or disconnect two contact points provided on a board such as a printed-wiring board, a pushbutton switch is known which comprises a switch button having a conductive member at its bottom, and a base plate molded integrally with the switch button for supporting the switch button such that the switch button can be moved vertically. The pushbutton switch is placed on the board having the two contact points such that the conductive member is positioned opposite to the two contact points. The two contact points can be easily connected to or disconnected from each other using the pushbutton switch. The contact points are connected by pressing down the switch button and are disconnected by stopping the pressing of the switch button.
In such a pushbutton switch, when the switch button is obliquely pressed from the upper side, the conductive member and the contact points are insufficiently connected. To prevent this, the conductive member is made of elastic material such as silicone rubber, or alternatively a guide member is provided for guiding the movement of the switch button such that the switch button is not inclined by oblique pressing. Even so, such a pushbutton switch has a problem. Since the conductive member is directly attached to the switch button, vibration, which is transmitted from a fingertip or generated on the switch button when pushed hard, adversely affects the conductive member. When this happens, chattering may be caused, that is to say, the contact points are repeatedly connected to or disconnected from each other due to the vibration.
To solve the above problem, U.S. Pat. No. 3,699,293 proposes a key switch in which a conductive member is attached to a switch button via a spring such as coil spring. The vibration caused when the switch button is pushed is absorbed by the spring and the conductive member is securely pressed onto the contact points by the energization of the spring. However, since the energization of the spring is used to keep close contact between the conductive member and the contact points, such a key switch should be provided with a controlling member for controlling the movement of the conductive member such that the conductive member may not touch the contact points while the switch button is not pushed. In addition to the controlling member, a guide member is required to prevent insufficient contact between the conductive member and the contact points, which happens, for example, when the switch button is obliquely pushed and thus the conductive member moves away from the contact points. Consequently, such a pushbutton switch has a complicated structure and high productivity and durability cannot be attained.